Iād love to vote for Yaz and Belinda, but Dan and Ruby just pip them to the top spots. I think if weād had more character exploration of Yaz, or Belindaās initial characterisation had been followed through, I would have had a lot more difficulty choosing. As it is, I think Danās just a great, funny take on the everyman companion archetype, and Ruby is fantastically played by Millie Gibson and gets lots of chances to shine in stories like 73 Yards, Lucky Day and The Reality War.
If I was being uncharitable Iād say none of the above 
Belinda is probably my favourite of this list - or at least the Belinda who lives in my head is anyway
For anyone wondering, I left the likes of Donna and Mel off the list in order to stick to ānewā 2020s-era companions.
Belinda, but with the caveat of desperately blocking out the reality war. Dan is also cool
Does Joy really count?
All she did was turn into a star.
But iām going with Yaz and Ruby.
Belinda if i had a 3rd vote - despite having her whole character changed
Ruby is definitely my favourite of them. After that is probably Belinda but I was a bit disappointed by her. Not that big of a fan of any of the 13thās companions and the rest donāt feel like companions
Personally, I think the issues with Belinda start one episode earlier, when she has no reaction to the Doctor torturing Kid in The Interstellar Song Contest - episode one Belinda would have torn him a new one for that, but instead she just looks mildly shocked, gives him a hug and tells him heās wonderful just a few scenes later, and I donāt really like that. The companion role works best when theyāre challenging the Doctor and offering a human perspective to counterbalance that dark side, and I think that element is completely ignored in that episode. I would have loved something like (late monthly range Fifth Doctor audio spoiler) Conversion, where Tegan is explicitly appalled by the satisfaction the Doctor takes from dispatching some Cybermen. Then of course thereās just about everything with Belinda in the finale two-parter, as you say.
I went for Graham and Ruby, I really like both of them and whilst I didnāt like Rubyās exit/story reveal in the finale, unlike Belinda it didnāt take away from the character weāve grown to love.
I donāt consider Anita, Rose, Joy or even Karvanista companions, although Karvanista was one in the past.
Ruby definitely takes this for me - perhaps the best developed and most rounded character of Daviesā return - absolutely loved all she does.
Yaz would be just behind in second place, aided by her longevity, and a great dynamic with the Doctor.
I do think though that generally this has been a disappointing decade for companions, not reaching the heights of Davies and Moffatās work in the 00s and 10s, or the peaks of companions from the classic era.
I donāt love with any revival companions the way I love Classic or EU companions, so this was hard, because I feel pretty much the same about all these characters. I ended up voting for Yaz and Dan, because I really enjoyed them together in Flux. Iām looking forward to see what BF does with Yaz, because I think she has a lot of potential to be great!
If they didnt ruin Belinda in like last 4 episodes then her,but Dan and Graham clear.
Ruby, I guess? I think Gibson is a wonderful performer even if the character is about as deep as a puddle.
Honestly, looking at this list, there really isnāt a single character that stands out. A couple are just fine, the rest rank amongst my least favourite companions ever.
Strange thing about Ruby is that I like her a lot when sheās not a companion but Iām not sure whether that really applies to her as a companion, as I think sheās a lot less interesting when sheās with the Doctor.
Sheād actually be a good focus character for UNIT type spinoffs.
I really wanted to vote for Belinda but I donāt think she was written to fulfill her potential past The Well. And, well, I just adored Karvanista.
Yeah, thatās the trouble. She started off great, and then turned into a generic companion, and then was rewritten to be a mother. If sheād stayed the way she was early on, thereād be no trouble voting for her, but she doesnāt really end up staying the same character.
I love practically all of these companions 
(Belinda I will never forgive Russell for what he fid to you)
Joy is fine.
I really like Anita in Joy to the World, donāt care for her in the Reality War.
Rose Noble is lovely, but I feel like I need to see more of her to really make my Mind up.
I like Graham, he cool 
I like Ryan, heās just a guy and thatās nice
Belinda is a weird one, I REALLY like her in the first 3 Episodes, donāt really like how she ended up and that really does affect my Opinion on her, if certain Things were different with her in the other last 4 Episodes, I might put her as my favorite of the Decade.
Karvanista is great, I love him, but I need more of him before I can get a full Opinion on him, lovely one tho!
Dan is a very nice Character, I quite like Dan, he is funny, and he got a good laugh out of me, when he became evil and started to eat the Universe, I CRIED!
Ruby is great, while at times a bit generic I think Millie does a great Job in the Role, especially in 73 Yards, so my first Vote goes to her, even if I have some Issues with certain Aspect of her Story, as far as her Character is concern I think she doesnāt get a massive whiplash like Belinda does.
Yaz is probably my favorite of the Decade, I just really like Mandip and I think her being in the entire Run from 13 does help her a lot compared to all the other 13 Companions. Very excited to see what BF does with her come next Month!!
Graham and Belinda [1]. This was tough since I like most of the 13th Doctor companions and all of 15ās.
Iām ignoring the finale for this ā©ļø
Thatās odd, I keep scrawling āValarie Lockwoodā on the screen, but the poll wonāt accept it.